Roy describes the system -- called Lumenoise
-- as a "playful and performative device" which lets you manipulate
abstract geometric patterns and sounds directly onto the screen
using a specially-devised light-sensing pen. He created the system
during a two week residency at La Gaîté Lyrique in Paris.

These days it's not unusual to interact with screens using
styluses, but CRT screens aren't touch sensitive. Roy took
advantage of the particular way that a CRT displays images -- by
filling the screen with a series of horizontal lines from top to
bottom dozens of times per second. The light-sensing pen, when
placed on the screen, can detect the exact moment at which the
electron beam -- which creates the lines that make up the image --
passes underneath it. This event gives you a set of coordinates
that tell you the position of the pen on screen. This information
is fed into a microcontroller, which then relays the positioning
information of the pen to the images on screen.

The particular program that Roy built featured four vertical
panels on the screen. Depending on where on the screen you placed
the pen, the CRT synthesiser would produce different sounds and
graphics. Each of the four panels produced different graphic
effects and the sound could be manipulated by moving the pen along
the vertical axis.

Roy is keen to share the joys of CRT screen hacking and has made
all of the code and schematics available to download via
his website. The circuit only used a few parts build around an
ATmega8 microcontroller -- all of which Roy fitted into his pen.
The project was coded in AVR-GCC.

Roy told Wired.co.uk: "Most people have experienced CRT screens
as a one way road for information. This is a simple tool to make
the screen become interactive. I find this somehow magic. They are
so big and ugly and heavy but they are so simple to understand.
They have a sort of secret underdog power which lets them do
something that a flat screen can't do without a touch-sensitive
surface."

Check out the video below. The grey square corresponds to the
position of the light-sensing pen. The project echoes that of the Wobbulator, which Wired.co.uk covered last year.